Parasitic nematodes infect over half of the world's human population and also reduce agricultural productivity by more than US$100 billion annually. The most harmful human pathogens are Ascaris lumbricoides, Ancylostoma duodenale, Necator americanus, Trichuris trichiura and Strongyloides stercoralis. These pathogens infect more than 3 billion people causing malnutrition, obstructive intestinal disease and substantial morbidity particularly among school age children (˜125,000 deaths each year) (Pearson, Current Infection Disease Report 4:59–64 (2002)). This will be aggravated in the future by lack of vaccines, limited chemical approaches, and the rapid increase in resistance to antihelmintic drugs (DeClercq et al., Am J Trop Med and Hygiene 57: 25–30 (1997), Hotez et al. Immunological Reviews 171: 163–171 (1999), Crompton, Adv. Parasitology 48: 285–375 (2001). Resistance to dehydration plays a key role in parasitic nematode epidemiology (Pit et al. Ann Trop Med Parasit 94: 165–171 (2000), Solomon et al. Parasitology 119: 621–626 (1999), Solomon et al. J Parasitology 84: 802–805 (1998), Solomon et al Int J Parasitology 27: 1517–1522 (1997)).
Contrary to human and animal parasitic nematodes, beneficial nematodes (Steinernematidae and Heterorhabditidae) are sensitive to dessication stress and other environmental constraints (Solomon et al., Nematology 1: 61–68 (1999), Kaya, Annual Review of Entomology 38: 181–206, (1993)). These nematodes are among the most promising alternatives to the chemical control of insect pests. They can actively locate, infect and kill a wide range of insect pest with the cooperation of a symbiotic bacterium (Xenorhababdus spp. and Photorhabdus spp.), and yet are safe for plants and animals.
Thus, there is a great need for understanding and modifying water stress tolerance of these and other organisms, for example, by decreasing water stress tolerance of pathogenic nematodes, and by increasing water stress tolerance of beneficial nematodes.